PB-1920: Fix AttributeError: '_thread._local' object has no attribute 'data' - #patch

[msom]

Currently, using the same ThreadMappingContext object in different threads throws a AttributeError: '_thread._local' object has no attribute 'data':

  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 376, in format
    message = self.formatMessage(record)
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 356, in formatMessage
    self._add_object_to_message(record, self.json_fmt, message)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 297, in _add_object_to_message
    message[key] = self._get_string_key_value(record, value)
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 343, in _get_string_key_value
    return style.format(record)
           ~~~~~~~~~~~~^^^^^^^^
  File "/usr/lib/python3.13/logging/__init__.py", line 472, in format
    return self._format(record)
           ~~~~~~~~~~~~^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 114, in _format
    dct = {**record.__dict__, **flatten_dict(record.__dict__)}
                                ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 44, in flatten_dict
    return dict(_flatten_dict_gen(dct, parent_key, sep))
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 376, in format
    message = self.formatMessage(record)
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 356, in formatMessage
    self._add_object_to_message(record, self.json_fmt, message)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 297, in _add_object_to_message
    message[key] = self._get_string_key_value(record, value)
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 343, in _get_string_key_value
    return style.format(record)
           ~~~~~~~~~~~~^^^^^^^^
  File "/usr/lib/python3.13/logging/__init__.py", line 472, in format
    return self._format(record)
           ~~~~~~~~~~~~^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 114, in _format
    dct = {**record.__dict__, **flatten_dict(record.__dict__)}
                                ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 44, in flatten_dict
    return dict(_flatten_dict_gen(dct, parent_key, sep))
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 38, in _flatten_dict_gen
    yield from flatten_dict(value, new_key, sep=sep).items()
               ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 44, in flatten_dict
    return dict(_flatten_dict_gen(dct, parent_key, sep))
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 35, in _flatten_dict_gen
    for key, value in dct.items():
                      ~~~~~~~~~^^
  File "<frozen _collections_abc>", line 898, in __iter__
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/context/thread_context.py", line 35, in __iter__
    return self.__local.data.__iter__()
           ^^^^^^^^^^^^^^^^^
AttributeError: '_thread._local' object has no attribute 'data'
", line 38, in _flatten_dict_gen
    yield from flatten_dict(value, new_key, sep=sep).items()
               ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 44, in flatten_dict
    return dict(_flatten_dict_gen(dct, parent_key, sep))
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/formatters/json_formatter.py", line 35, in _flatten_dict_gen
    for key, value in dct.items():
                      ~~~~~~~~~^^
  File "<frozen _collections_abc>", line 898, in __iter__
  File "/home/ltsom/Documents/repos/mf-chsdi3/.venv/lib/python3.13/site-packages/logging_utilities/context/thread_context.py", line 35, in __iter__
    return self.__local.data.__iter__()
           ^^^^^^^^^^^^^^^^^
AttributeError: '_thread._local' object has no attribute 'data'

Seems like the constructor is only executed in the thread the object is actually created but not in the other ones - not sure if this was different in Python versions <3.9. I've added a small helper that ensures that the self.__local objects have a data attribute before reading / writing. I've also added a test that actually tests if the data is thread-local (and that now passes without AttributeError).